Obviously an open cover is going to allow the clutch to cool better and vent the waste product (dust) to atmosphere. Noisy though they are, unless you religiously clean out the cover, then sooner or later you will suffer some detrimental effects of clutch dust (clogging, grabbing, screeching, dragging, slipping etc.)
If you're anti noise then stay closed but clean out regularly. For now give it a clean and see what it does, but in reality the clutch plate change is a piece of cake, just make sure you keep the metal plates in the same order!! Good luck
